Conservation of Chevalier's 'Cooks Straits'

Constructing the Frame

The design and construction of the frame for Chevalier's Cook Straits was executed by Matthew O'Reilly, Framer of Paintings, who also authored this article.

1. Cook Straits by Nicholas Chevalier was purchased by Te Papa in 2003. The painting arrived at Te Papa clad only in its original slip-frame. As it was produced in England in the 1880s, the painting would have originally been framed with another larger moulding. It was decided to design and build a new frame which would properly support and protect the painting but would also be in keeping with the original framing aesthetic.

2. This frame was chosen as a model for the new Chevalier frame. It was made for a painting of a similar scale and era – by Carlo Ruggeri. 3. This 1:1 scale drawing of the profile of the Ruggeri frame began the design process

4. A full sample corner of the new frame was manufactured so that every aspect of its design could be tested on the painting, and the best production method planned. This is especially important when frames such as this, have complicated production processes and are comprised of separate wooden components.

5. Constructing the frame

i. WoodTawhai (silver beech) was selected as the material for the new frame. Rough boards for the various frame parts were milled flat and smooth in suitable dimensions, and finally laminated together. The various curved surfaces were shaped with a spindle-moulder.

ii. GessoSeveral coats of gesso were next brushed onto the wooden surfaces and sanded flat.

The five decorative motifs of the Ruggeri frame were replicated in a three-step process. First, temporary moulds of the patterns were made in modelling clay. Next permanent wooden moulds were made from the temporary ones by carving the designs in the negative into fruit wood. Finally traditional compo was pressed into the wooden moulds to cast the different low relief motifs.

Once the desired relief motif was firmly pressed in the compo, the excess was cut away and the motif removed from the mould. The base of the compo relief was steamed to activate its glues and then carefully laid in place on the wood. The process was repeated for each different moulding.

Only the taenia was water-gilded. It was then burnished, and partially rubbed back to reveal the bole colour.

v. 2 Oil gildingThe remainder of the frame was oil gilded in another three-step process.

Firstly shellac tinted with yellow dye was brushed on to the gesso and compo reliefs to provide a yellow impermeable under-surface. Later a twelve-hour size was applied with a brush and then gilded during its open period approximately 12-17 hours later.

Being careful to avoid the water gilded area, the oil gilding was sealed with a very thin coat of shellac. Dry pigments were next mixed into a clear matte picture varnish to a desired tint, and beeswax added. After the sealant had dried, this thick mixture was then selectively dabbed on to the frame’s surface and quickly rubbed away. This brought up the highlights in the different relief elements of the frame and gave it a consistent overall patina.

Before adding the painting to the frame, the face of the rabbet had to be lined to minimise abrasion to the paint surface which would be in contact with the frame.

The painting could then be placed in its new frame. After it was correctly positioned, spacers were cut from short lengths of balsa wood and fixed between the edges of the rabbet and the painting to prevent any movement.

Brass mirror plates were screwed to the back of the frame and angled to hold the painting in place and a backboard was attached over the back of the painting. To complete the process and enable the secure hanging of the work in storage and during exhibitions, stainless steel marine cleats and security fittings were also fixed to the back of the frame. Viola!

Frame: A picture frame has traditionally served two functions: protecting the painting in its environment as well as complementing the aesthetic qualities of the painting through its form and materials.

Protecting the paintingA frame needs to provide sufficient structure to prevent the painting from flexing, and to absorb possible knocks, impacts or abrasions. Frames almost always project forward of the paint surface. They carry the hardware that fixes the painting to the wall, and glazing as required.

A slip-frame is traditionally a component of a larger framing system and provides a protective buffer between other heavier mouldings and the painting. Usually made from a plain moulding, it directly contains the painting. Any other mouldings are layered around it. Slip-frames came into use in the 19th century.

Wood: Picture frames have traditionally been made from wood. This remains the favoured material though aluminium is also used. Internationally some favoured wood-types have been lime, oak, poplar, box wood and some types of pine. These timbers are hard to obtain in New Zealand and instead slower growing pines have been used especially where gold leaf and/or plasterwork are to be applied. When complex surfaces and finishes are required, frames are constructed at Te Papa from tawhai/silver beech (Nothofagus menziesii).

A spindle moulder is a table machine with a vertically set, fast-spinning spindle onto which a blade is fastened which can cut wood to any desired shape.

Gesso derives from the Italian word for gypsum i.e. anhydrous calcium sulphate. In most European countries, as well as the U.S., Australia and New Zealand, the use of whiting (calcium carbonate) is more common. Liquid gesso is made using one of the two mixed with rabbit skin glue. Gesso is a traditional ground for use under oil paint. When used on frames, it can be rubbed or cut back to the desired form and texture once dry. An important effect of gesso is to disguise the grain of wood. It can also be tooled to give precise textures especially important where gold or silver leaf is to be added.

Compo short for composition plaster, is a thermo-plastic material used for casting motifs in relief. When heated it becomes soft and pliable and can be pressed into a mould, or draped over curved wooden mouldings to gain the impression of the frame surface underneath. It is made from a mixture of whiting (see gesso above), linseed oil, tree resin, hide glue and rabbit skin glue.

Decorative motifs are the parts of the frame profile that have a three dimensional pattern on the surface. These embellishments may be carved directly into the wood or cast from compo and applied to the surface of the wooden structure.

Bole is a coloured clay that is commonly used under gold or silver leaf to enhance the appearance of gilded surfaces. It is mixed with rabbit skin glue and can be burnished so that the gold leaf applied to it, shines like a mirror. Sometimes the bole colour is allowed to show through beneath the leaf to contribute depth and variety to the colour. Like gesso, it is brushed on and usually sanded smooth.

GildingGilding is the process of applying gold or silver leaf. Most gold leaf is between 18 and 24 carats (24 ct being pure). Minute amounts of other metals such as silver and copper can be added to create subtle differences in colour. Typically it has an average thickness of .5 micron (.0005mm). As the leaf is extremely delicate, it is transferred from the manufacturer’s book to a “gilder’s cushion” where it is cut to size with a special knife. From there, it is picked up with purpose-made flat brush called a “tip” and transferred to the desired position on the frame.

Matthew O'Reilly, Framer of Paintings, with gold leaf.

There are two main gilding techniques – water-gilding and oil-gilding.

Water-gilding is the highest quality of gilding. It is known as water-gilding because the gold is laid onto a wet surface – the glues in the bole are activated by the water and ensure that the gold sticks. Water-gilding is faithful to any surface decoration but is time consuming as preparation must be thorough to achieve the best effects.

Oil-gilding is widely used as it takes less time than water-gilding and can be applied to many different surfaces. The under surface is first sealed with a varnish often tinted yellow so that any small breaks in the gold leaf will not be visible. Next a slow drying oil size (a mixture of linseed and other oils) is brushed on. The leaf is then added in the same manner as described in the gilding process.

Shellac is a traditional varnish and sealant made from the secretion of the female lac beetle (kerria lacca) found in Eastern India and Thailand. In dried form, the shellac is dissolved in alcohol for application. Shellac is used in French polishing.

Oil size in this context refers to the glue or adhesive used in oil-gilding. The size is made with oils including linseed which are formulated to dry over specific periods of time – commonly used options are three, twelve and twenty-four hour size formulations. Gold or silver leaf can be applied when the size is dry enough so that the surface texture is not disturbed and wet enough for the leaf to stick. This period when the gilding can take place is known as the open period.

Burnishing polishes the frame by smoothing the gilded areas with a special tool made from an agate stone set on a handle. It adds lustre and brightness.

Patina is the gloss on the surface of woodwork produced by age but which can also be produced artificially in the gilding process.

Outfitting and setting the painting into the frame: To protect the painting, it must be held securely within the frame, but not so tightly that it cannot breathe i.e. expand and contract normally during changes in humidity. Giving the painting this space minimises possible stress to its structure. Furthermore as the painting is not perfectly square, the fit within the rabbet must be generous to accommodate this.

Rabbet or rebate is an L-shaped cavity at the back of the frame which holds the painting around all its edges.

Mirror plates are flat pieces of shaped metal that were invented to attach a mirror’s frame to the wall in a system which allows screws to be inserted in both the wall and the back of the frame. Mirror plates are among materials used in setting paintings into frames because they can be readily bent to apply light pressure against the back of a painting without actually attaching to the painting itself.

Backboard is a thin sheet of material such as acrylic or hardboard, corrugated polypropylene or the like, attached to the back of the frame to protect the painting from impact, to prevent an accumulation of dust and minimise any potential for damage during transportation.

Marine cleats are fittings which were developed for yachts. They enable the tension and release of ropes. However they are also useful for hanging paintings because of their strength and shape which is ideal for slipping over nails or screws attached to the wall.